KR101753391B1 - Method and apparatus of transmitting signal in wireless communication system - Google Patents

Method and apparatus of transmitting signal in wireless communication system Download PDF

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KR101753391B1
KR101753391B1 KR1020100024043A KR20100024043A KR101753391B1 KR 101753391 B1 KR101753391 B1 KR 101753391B1 KR 1020100024043 A KR1020100024043 A KR 1020100024043A KR 20100024043 A KR20100024043 A KR 20100024043A KR 101753391 B1 KR101753391 B1 KR 101753391B1
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signal
precoding
resource
bandwidth
channel
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KR1020100024043A
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Korean (ko)
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KR20100109387A (en
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이문일
이욱봉
구자호
고현수
정재훈
임빈철
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엘지전자 주식회사
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413MIMO systems
    • H04B7/0456Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00Arrangements for detecting or preventing errors in the information received
    • H04L1/004Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0041Arrangements at the transmitter end
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00Arrangements for detecting or preventing errors in the information received
    • H04L1/004Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0075Transmission of coding parameters to receiver
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00Arrangements for detecting or preventing errors in the information received
    • H04L1/02Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00Baseband systems
    • H04L25/02Details ; Arrangements for supplying electrical power along data transmission lines
    • H04L25/03Shaping networks in transmitter or receiver, e.g. adaptive shaping networks ; Receiver end arrangements for processing baseband signals
    • H04L25/03006Arrangements for removing intersymbol interference
    • H04L25/03343Arrangements at the transmitter end
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00Arrangements affording multiple use of the transmission path
    • H04L5/003Arrangements for allocating sub-channels of the transmission path
    • H04L5/0048Allocation of pilot signals, i.e. of signals known to the receiver
    • H04L5/0051Allocation of pilot signals, i.e. of signals known to the receiver of dedicated pilots, i.e. pilots destined for a single user or terminal
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W88/00Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02Terminal devices
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W88/00Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/08Access point devices

Abstract

A method and apparatus for signal transmission in a wireless communication system are provided. The method includes generating R spatial streams, each of the R spatial streams being generated based on an information stream and a reference signal, generating N transport streams based on the R spatial streams and the precoding matrix, Mapping the N transport streams to at least one resource block and generating N signals from the N transport streams mapped to the at least one resource block, And transmitting through each of the N antennas.

Description

Field of the Invention [0001] The present invention relates to a method and apparatus for transmitting a signal in a wireless communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wireless communication, and more particularly, to a method and apparatus for transmitting a signal in a wireless communication system.

Background of the Invention [0002] Wireless communication systems are widely deployed to provide various types of communication services such as voice and data. The purpose of a wireless communication system is to allow multiple users to communicate reliably regardless of location and mobility. However, a wireless channel is a wireless channel that is affected by path loss, noise, fading due to multipath, intersymbol interference (ISI) (Doppler effect). Accordingly, various technologies have been developed to overcome the non-ideal characteristics of the wireless channel and to increase the reliability of the wireless communication.

There is a multiple input multiple output (MIMO) technique to support reliable, high-speed data services. The MIMO scheme improves the transmission and reception efficiency of data by using multiple transmit antennas and multiple receive antennas. MIMO schemes include spatial multiplexing, transmit diversity, and beamforming.

A MIMO channel matrix is formed by multiple receive antennas and multiple transmit antennas. A rank can be obtained from the MIMO channel matrix. The rank is the number of spatial layers. The rank may be defined as the number of spatial streams that a transmitter can simultaneously transmit. The rank is also called the spatial multiplexing rate. When the number of transmission antennas is Nt and the number of reception antennas is Nr, the rank R becomes R? Min {Nt, Nr}.

In a wireless communication system, a signal known to both a transmitter and a receiver is required for channel measurement, information demodulation, and the like. A signal known to both the transmitter and the receiver is referred to as a reference signal (RS). The reference signal may also be referred to as a pilot.

The receiver can estimate the channel between the transmitter and the receiver through the reference signal and demodulate the information using the estimated channel. When a terminal receives a reference signal transmitted from a base station, the terminal measures a channel through a reference signal and can feedback channel state information to the base station.

Since a signal transmitted from a transmitter undergoes a channel corresponding to each transmit antenna or each spatial layer, a reference signal can be transmitted for each transmit antenna or for each spatial layer. When the reference signal is transmitted on a spatial layer basis, the reference signals may be precoded and transmitted. In this case, the receiver needs to know information about the frequency domain in which the same precoding matrix is used.

Therefore, there is a need to provide an efficient signal transmission method and apparatus in a wireless communication system.

SUMMARY OF THE INVENTION The present invention provides a signal transmission method and apparatus in a wireless communication system.

In one aspect, a method of signal transmission in a wireless communication system is provided. The method includes generating R spatial streams, each of the R spatial streams being generated based on an information stream and a reference signal, generating N transport streams based on the R spatial streams and the precoding matrix, Mapping the N transport streams to at least one resource block and generating N signals from the N transport streams mapped to the at least one resource block, And transmitting through each of the N antennas.

In another aspect, a signal transmission apparatus is provided in a wireless communication system. The apparatus includes N antennas and N antennas to transmit precoding bandwidth information indicating a bandwidth in which the same precoding matrix is used and to generate R spatial streams, Stream and a reference signal, generating N transport streams based on the R spatial streams and a precoding matrix, mapping the N transport streams to at least one resource block, Generates N signals from the N transport streams mapped to the block, and transmits each of the N signals through each of the N antennas.

An efficient signal transmission method and apparatus in a wireless communication system can be provided. Thus, overall system performance can be improved.

1 is a block diagram illustrating a wireless communication system.
2 shows an example of a radio frame structure.
3 is an exemplary diagram illustrating a resource grid for one downlink slot.
4 shows an example of the structure of the downlink subframe.
5 shows an example of mapping of a common reference signal to one antenna in the case of a normal CP.
6 shows an example of mapping common reference signals for two antennas in case of a normal CP.
7 shows an example of mapping of common reference signals for four antennas in case of a normal CP.
8 shows an example of a mapping of a common reference signal to one antenna in the case of an extended CP.
9 shows an example of mapping of common reference signals for two antennas in the case of an extended CP.
10 shows an example of a mapping of common reference signals for four antennas in case of an extended CP.
11 shows an example of mapping of a dedicated reference signal in case of a normal CP in LTE.
12 shows an example of mapping of dedicated reference signals in case of CP extended in LTE.
13 is a block diagram showing an example of a transmitter structure.
14 is a block diagram showing an example of the information processor structure of FIG.
15 is a block diagram illustrating an example of a transmitter structure that generates a non-precoded dedicated reference signal.
16 is a block diagram illustrating an example of a transmitter structure for generating a precoded dedicated reference signal.
17 is a block diagram illustrating an example of a device for wireless communication in which a precoded dedicated reference signal is used.
18 is a flowchart illustrating a signal transmission method in a wireless communication system according to an embodiment of the present invention.
Figure 19 shows an example of a feedback subband for a single PMI type.
Figure 20 shows an example of a precoding subband for a single PMI type.
Figure 21 shows an example of a feedback subband for the case of multiple PMI types.
Figure 22 shows an example of precoding subbands for multiple PMI types.
23 shows an example of the precoding bandwidth.
24 is a block diagram illustrating an apparatus for wireless communication in which an embodiment of the present invention is implemented.

The following description is to be understood as illustrative and not restrictive, with reference to the accompanying drawings, in which: FIG. 1 is a block diagram of a mobile communication system according to an embodiment of the present invention; And may be used in a variety of multiple access schemes as well. CDMA may be implemented in radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. The TDMA may be implemented in a wireless technology such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in wireless technologies such as IEEE (Institute of Electrical and Electronics Engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and Evolved UTRA (E-UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) is a part of E-UMTS (Evolved UMTS) using E-UTRA, adopting OFDMA in downlink and SC-FDMA in uplink. LTE-A (Advanced) is the evolution of LTE.

In order to clarify the description, LTE (Release 8) / LTE-A (Release 10) is mainly described, but the technical idea of the present invention is not limited thereto.

1 is a block diagram illustrating a wireless communication system.

Referring to FIG. 1, a wireless communication system 10 includes at least one base station 11 (BS). Each base station 11 provides a communication service to a specific geographical area (generally called a cell) 15a, 15b, 15c. The cell may again be divided into multiple regions (referred to as sectors). A user equipment (UE) 12 may be fixed or mobile and may be a mobile station, a user terminal (UT), a subscriber station (SS), a wireless device, a personal digital assistant (PDA) A wireless modem, a handheld device, and the like. The base station 11 generally refers to a fixed station that communicates with the terminal 12 and may be referred to by other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, have.

Hereinafter, downlink (DL) means communication from a base station to a terminal, and uplink (UL) means communication from a terminal to a base station. In the downlink, the transmitter may be part of the base station, and the receiver may be part of the terminal. In the uplink, the transmitter may be part of the terminal, and the receiver may be part of the base station.

A wireless communication system may support multiple antennas. The transmitter may use multiple transmit antennas, and the receiver may use multiple receive antennas. A transmit antenna means a physical or logical antenna used to transmit a signal or a stream and a receive antenna means a physical or logical antenna used to receive a signal or a stream. If the transmitter and receiver use multiple antennas, the wireless communication system may be referred to as a multiple input multiple output (MIMO) system.

The process of wireless communication is preferably implemented as a plurality of independent layers of hierarchy rather than being implemented as a single layer. A plurality of vertical hierarchical structures is called a protocol stack. The protocol stack can refer to an open system interconnection (OSI) model, which is a model for a protocol structure well known in communication systems.

2 shows an example of a radio frame structure.

Referring to FIG. 2, a radio frame is composed of 10 subframes, and one subframe is composed of two slots. Slots in radio frames are numbered from # 0 to # 19. The time taken for one subframe to be transmitted is called a transmission time interval (TTI). TTI is a scheduling unit for information transmission. For example, the length of one radio frame is 10 ms, the length of one subframe is 1 ms, and the length of one slot may be 0.5 ms. The structure of the radio frame is merely an example, and the number of subframes included in a radio frame or the number of slots included in a subframe can be variously changed.

3 is an exemplary diagram illustrating a resource grid for one downlink slot.

3, a downlink slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a time domain and an N_DL resource block (RB) in a frequency domain . An OFDM symbol is used to represent one symbol period and may be called another name such as an OFDMA symbol and an SC-FDMA symbol according to a multiple access scheme. The number N_DL of resource blocks included in the downlink slot is dependent on the downlink transmission bandwidth set in the cell. In LTE, N_DL may be any of 6 to 110. One resource block includes a plurality of subcarriers in the frequency domain.

Each element on the resource grid is called a resource element. The resource element on the resource grid can be identified by an index pair (k, l) in the slot. Here, k (k = 0, ..., N_DL x 12-1) is a frequency-domain subcarrier index, and l (l = 0, ..., 6) is a time domain OFDM symbol index.

Here, one resource block exemplarily includes 7 × 12 resource elements including 7 OFDM symbols in the time domain and 12 subcarriers in the frequency domain, but the number of OFDM symbols and the number of subcarriers in the resource block are But is not limited to. The number of OFDM symbols can be variously changed according to the length of a CP (cyclic prefix) and the subcarrier spacing. For example, the number of OFDM symbols in a normal CP is 7, and the number of OFDM symbols is 6 in an extended CP.

The resource grid for one downlink slot of FIG. 3 may also be applied to a resource grid for an uplink slot.

4 shows an example of the structure of the downlink subframe.

Referring to FIG. 4, the downlink subframe includes two consecutive slots. The 3 OFDM symbols preceding the 1st slot in the DL subframe are control regions and the remaining OFDM symbols are data regions. Here, it is only an example that the control region includes 3 OFDM symbols.

A data downlink shared channel (PDSCH) may be allocated to the data area. Downlink data is transmitted on the PDSCH.

A control channel such as a physical control format indicator channel (PCFICH), a physical hybrid automatic repeat request (PHICH) indicator channel, or a physical downlink control channel (PDCCH) may be allocated to the control region.

The PCFICH carries information on the number of OFDM symbols used for transmission of the PDCCHs in the subframe to the UE. The number of OFDM symbols used for PDCCH transmission can be changed every subframe. The PHICH carries HARQ ACK (acknowledgment) / NACK (negative acknowledgment) for the uplink data.

The PDCCH carries downlink control information. The downlink control information includes downlink scheduling information, uplink scheduling information, or uplink power control commands. The downlink scheduling information is also referred to as a downlink grant, and the uplink scheduling information is also referred to as an uplink grant.

The downlink grant may include a resource allocation field indicating a time-frequency resource to which downlink data is transmitted, an MCS field indicating a modulation coding scheme (MCS) level of downlink data, and the like.

If the transmission scheme is MU-MIMO (multiple user-MIMO), the downlink grant may further include a power offset field. The power offset field indicates power offset information for obtaining downlink transmission energy per resource element.

The transmission scheme is a scheme in which a base station transmits downlink data to a mobile station. For example, the transmission scheme includes a single antenna scheme and a MIMO scheme. The MIMO scheme includes a transmit diversity scheme, a closed loop spatial multiplexing scheme, an open loop spatial multiplexing scheme, and an MU-MIMO scheme. The transmission scheme can be set semi-statically by higher layer signaling, such as radio resource control (RRC).

In a wireless communication system, a signal known to both a transmitter and a receiver is required for channel measurement, information demodulation, and the like. A signal known to both the transmitter and the receiver is referred to as a reference signal (RS). The reference signal may also be referred to as a pilot. The reference signal can be generated in the physical layer without carrying information derived from the upper layer.

The reference signal can be transmitted multiplied by a predefined reference signal sequence. The reference signal sequence may be a binary sequence or a complex sequence. For example, the reference signal sequence may use a pseudo-random (PN) sequence, an m-sequence, or the like. However, this is only an example, and the reference signal sequence is not particularly limited. When the base station multiplies the reference signal by the reference signal sequence and transmits the resultant signal, the terminal can reduce the interference of the signal of the adjacent cell on the reference signal. This can improve channel estimation performance.

The reference signal may be divided into a common RS and a dedicated RS.

The common reference signal is a reference signal transmitted to all UEs in the cell. All terminals in the cell can receive a common reference signal. To avoid inter-cell interference, the common reference signal may be cell-specific. In this case, the common reference signal is also referred to as a cell-specific RS. The common reference signal can be used for channel measurement and information demodulation. An example of a reference signal for channel measurement only is CSI-RS (channel state information-RS).

The dedicated reference signal is a reference signal received by a specific terminal or a specific terminal group in the cell. The other terminal can not use the dedicated reference signal. The dedicated reference signal is also referred to as a UE-specific RS. The dedicated reference signal may be transmitted through a resource block allocated for downlink data transmission of a specific UE. A dedicated reference signal can be used for information demodulation.

5 shows an example of mapping of a common reference signal to one antenna in the case of a normal CP. 6 shows an example of mapping common reference signals for two antennas in case of a normal CP. 7 shows an example of mapping of common reference signals for four antennas in case of a normal CP. 8 shows an example of a mapping of a common reference signal to one antenna in the case of an extended CP. 9 shows an example of mapping of common reference signals for two antennas in the case of an extended CP. 10 shows an example of a mapping of common reference signals for four antennas in case of an extended CP.

Referring to Figs. 5 to 10, Rp denotes a resource element used for transmitting a reference signal through an antenna #p (p = 0, 1, 2, 3). Hereinafter, a resource element used for reference signal transmission is referred to as a reference resource element. Rp is a reference resource element for antenna #p. Rp is not used for any transmission through all other antennas except antenna #p. In other words, a resource element used for transmission of a reference signal via an antenna in a subframe can be set to 0, not used for any transmission through another antenna in the same subframe. This is to avoid interference between the antennas.

Hereinafter, for convenience of description, the minimum unit of the reference signal pattern (RS pattern) in the time-frequency resource is referred to as a basic unit. The reference signal pattern is a method in which the position of a reference resource element is determined in a time-frequency resource. When the basic unit is extended to the time domain and / or the frequency domain, the reference signal pattern is repeated. Here, the basic unit is one resource block in the frequency domain and one subframe in the time domain.

The common reference signal may be transmitted for each downlink subframe. One common reference signal is transmitted for each antenna. The common reference signal corresponds to a set of reference resource elements in a subframe. The base station may multiply the common reference signal by a predefined sequence of common reference signals and transmit.

The reference signal pattern of the common reference signal is referred to as a common reference signal pattern. The common reference signal patterns for each of the antennas are orthogonal to each other in the time-frequency domain. The common reference signal pattern is common to all terminals in the cell. The common reference signal sequence is also common to all UEs in the cell. However, in order to minimize inter-cell interference, each of the common reference signal pattern and the common reference signal sequence may be determined according to the cell.

The common reference signal sequence can be generated in OFDM symbol units in one subframe. The common reference signal sequence may vary depending on a cell ID, a slot number in one radio frame, an OFDM symbol index in a slot, a length of a CP, and the like.

In an OFDM symbol including a reference resource element in a basic unit, the number of reference resource elements for one antenna is two. That is, in the OFDM symbol including Rp in the basic unit, the number of Rp is 2. The subframe includes an N_DL resource block in the frequency domain. Therefore, the number of Rp in the OFDM symbol including Rp in the subframe is 2 x N_DL. The length of the common reference signal sequence for the antenna #p in the OFDM symbol including Rp in the subframe is 2 x N_DL.

The following equation shows an example of a complex sequence r (m) generated for a common reference signal sequence in one OFDM symbol.

Figure 112010017077108-pat00001

Here, N_max and DL are the number of resource blocks corresponding to the maximum downlink transmission bandwidth supported in the wireless communication system. In LTE, N_max and DL are 110. If N_DL is smaller than N_max, DL, a certain portion of the 2 × N_DL length of the complex sequence generated with 2 × N_max, DL length can be selected and used as a common reference signal sequence. c (i) is the PN sequence. The PN sequence may be defined by a Gold sequence of length-31. The following equation shows an example of c (i).

Figure 112010017077108-pat00002

Where Nc = 1600, x (i) is the first m-sequence, and y (i) is the second m-sequence. For example, the first m-sequence may be initialized to x (0) = 1, x (i) = 0 (i = 1, 2, ..., 30) at the beginning of each OFDM symbol . The second m-sequence may be initialized according to the cell ID at the beginning of each OFDM symbol, the slot number in the radio frame, the OFDM symbol index in the slot, the length of the CP, and the like.

The following equation is an example of initialization of the second m-sequence.

Figure 112010017077108-pat00003

Here, n_s is a slot number in a radio frame, l is an OFDM symbol index in a slot, and N_cell_ID is a cell ID. N_CP is 1 when it is a normal CP, and N_CP is 0 when it is an extended CP.

When generating the common reference signal sequence in this manner, the common reference signal sequence is independent of the antenna. Therefore, when a common reference signal is transmitted for each of a plurality of antennas in the same OFDM symbol, the common reference signal sequence of each of the plurality of antennas is the same.

The common reference signal sequence generated for each OFDM symbol including the reference resource element is mapped to the reference resource element according to the common reference signal pattern. In this case, the common reference signal sequence can be mapped to the reference resource element in ascending order of the subcarrier index in the N_DL resource block in the frequency domain in order. That is, the common reference signal can be transmitted over the entire frequency band. At this time, a common reference signal sequence is generated for each antenna, and a common reference signal sequence is mapped to each reference resource element for each antenna.

11 shows an example of mapping of a dedicated reference signal in case of a normal CP in LTE. 12 shows an example of mapping of dedicated reference signals in case of CP extended in LTE.

Referring to Figures 11 and 12, R5 represents a resource element used for dedicated reference signal transmission through antenna # 5. In LTE, a dedicated reference signal is supported for single antenna transmission. Only when the downlink data transmission scheme on the PDSCH by the upper layer is set to transmit a single antenna through antenna # 5, a dedicated reference signal may be present and may be valid for PDSCH demodulation. The dedicated reference signal may only be transmitted on the resource block to which the PDSCH is mapped. The dedicated reference signal corresponds to a set of reference resource elements in the resource block to which the PDSCH is mapped. The base station may multiply the dedicated reference signal by a predefined dedicated reference signal sequence and transmit the result. Here, the basic unit is one resource block in the frequency domain and one subframe in the time domain.

The dedicated reference signal can be transmitted simultaneously with the common reference signal. Therefore, the reference signal overhead becomes much higher than the reference signal overhead when only the common reference signal is transmitted. A terminal can use a common reference signal and a dedicated reference signal together. A terminal uses a common reference signal in a control region in which control information in a subframe is transmitted and a terminal can use a dedicated reference signal in a remaining data region in a subframe. For example, the control region is an OFDM symbol in which the OFDM symbol index l in the first slot of the subframe is 0 to 2 (see FIG. 4).

The dedicated reference signal pattern, which is a reference signal pattern of the dedicated reference signal, can be common to all terminals in the cell. However, in order to minimize the inter-cell interference, the dedicated reference signal pattern can be determined according to the cell. The dedicated reference signal sequence may be determined according to the UE. Therefore, only the specific terminal in the cell can receive the dedicated reference signal.

A dedicated reference signal sequence may be generated in units of subframes. The dedicated reference signal sequence may vary depending on the cell ID, the position of the subframe in one radio frame, the terminal ID, and the like.

The number of reference resource elements for a dedicated reference signal within a basic unit is 12. That is, the number of R5 in the basic unit is 12. When the number of resource blocks to which PDSCHs are mapped is N_PDSCH, the total number of R5s for dedicated RSs is 12 x N_PDSCH. Therefore, the length of the dedicated reference signal sequence is 12 x N_PDSCH. The length of the dedicated RS sequence may vary depending on the number of resource blocks allocated to the UE for PDSCH transmission.

The following equation shows an example of the dedicated reference signal sequence r (m).

Figure 112010017077108-pat00004

Here, c (i) is a PN sequence. (2) can be used for c (i). At this time, the second m-sequence may be initialized according to the cell ID at the beginning of each sub-frame, the position of the sub-frame in one radio frame, the terminal ID, and the like.

The following equation is an example of initialization of the second m-sequence.

Figure 112010017077108-pat00005

Here, n_s is a slot number in a radio frame, N_cell_ID is a cell ID, and UE_ID is a terminal ID.

The dedicated reference signal sequence is mapped to the reference resource element according to the reference signal pattern in the resource block to which the PDSCH is mapped. At this time, dedicated reference signal sequences are sequentially mapped to the reference resource elements in ascending order of the priority subcarrier index in the resource block, and then in ascending order of the OFDM symbol index.

Thus, dedicated reference signals in LTE are supported for single spatial streams and single antenna transmissions, while in LTE-A, dedicated reference signals must also be supported for multiple spatial streams or multiple antenna transmissions. Therefore, there is a need to provide a dedicated reference signal transmission method and apparatus for multi-spatial stream or multi-antenna transmission.

Hereinafter, a method and an apparatus for transmitting information and dedicated reference signals through multiple antennas will be described in detail. The following description is applicable not only to the LTE-A system but also to a general OFDM-MIMO system.

13 is a block diagram showing an example of a transmitter structure. Here, the transmitter may be a terminal or a part of a base station.

13, the transmitter 100 includes an information processor 110, Nt resource element mapper 120-1, ..., 120-Nt, Nt OFDM signal generators signal generators 130-1 to 130-Nt and Nt RF units 140-1 to 140-Nt and Nt transmission antennas 190-1 to 190- ..., 190-Nt) (Nt is a natural number).

The information processor 110 is connected to each of the Nt resource element mappers 120-1, ..., 120-Nt. Each of the Nt resource element mappers 120-1 to 120-Nt is connected to each of the Nt OFDM signal generators 130-1 to 130-Nt, and the Nt OFDM signal generators 130 And 140-Nt are connected to Nt RF units 140-1 to 140-Nt and Nt RF units 140-1 to 140- Nt are respectively connected to Nt transmission antennas 190-1, ..., 190-Nt. That is, the resource element mapper #n 120-n is connected to the OFDM signal generator #n 130-n and the OFDM signal generator #n 130-n is connected to the RF unit #n 140-n , The RF unit #n 140-n is connected to the transmission antenna #n 190-n (n = 1, ..., Nt). For multi-antenna transmission, there is one resource grid defined for each transmit antenna.

The information processor 110 receives information. The information may be control information or data. The information may be in the form of a bit or a bit stream. The transmitter 100 may be implemented at the physical layer. In this case, the information may be from a higher layer such as a medium access control (MAC) layer.

The information processor 110 is configured to generate Nt transport streams (transport stream # 1, transport stream # 2, ..., transport stream #Nt) from the information. Each of the Nt transport streams includes a plurality of transmission symbols. The transmission symbol may be a complex-valued symbol obtained by processing information.

Each of the Nt resource element mappers 120-1, ..., and 120-Nt is configured to receive each of the Nt transport streams. That is, the resource element mapper #n 120-n is formed to receive the transport stream #n (n = 1, ..., Nt). The resource element mapper #n 120-n is configured to map the transport stream #n to the resource elements in the resource block allocated for information transmission. Each of the transmission symbols of the transport stream #n may be mapped to one resource element. A '0' may be inserted into a resource element to which the transport stream #n is not mapped.

There may be more than one resource block allocated for information transmission. When a plurality of resource blocks are allocated, the plurality of resource blocks may be allocated consecutively or discontinuously.

Each of the Nt OFDM signal generators 130-1, ..., 130-Nt is configured to generate a time-continuous OFDM signal for each OFDM symbol. Time-continuous OFDM signals are also referred to as OFDM baseband signals. Each of the Nt OFDM signal generators 130-1, ..., and 130-Nt may generate an OFDM signal by performing inverse fast Fourier transform (IFFT), CP insertion, or the like for each OFDM symbol.

Each of the Nt RF units 140-1 to 140-Nt converts each OFDM baseband signal into a radio signal. The OFDM baseband signal may be upconverted to a carrier frequency and converted into a radio signal. The carrier frequency is also referred to as the center frequency. The transmitter 100 may use a single carrier or may use multiple carriers.

Each radio signal is transmitted through each of the Nt transmission antennas 190-1, ..., and 190-Nt.

14 is a block diagram showing an example of the information processor structure of FIG.

Referring to FIG. 14, the information processor 200 includes Q channel encoders 210-1 to 210-Q, Q scramblers 220-1 to 220-Q Q modulation mapper 230-1, ..., 230-Q, a layer mapper 240, and a precoder 250. The modulation mapper 230-1,

Each of the Q channel encoders 210-1 to 210-Q is connected to Q scramblers 220-1 to 220-Q, and Q scramblers 220-1 to 220- ..., and 230-Q are connected to a plurality of modulation mappers 230-1 to 230-Q, respectively, and a plurality of modulation mappers 230-1 to 230- (240), and the layer mapper (240) is connected to the precoder (250).

The precoder 250 is connected to Nt resource element mappers (see FIG. 5). That is, the channel encoder #q 210-q is connected to the scrambler #q 220-q and the scrambler #q 220 -q is connected to the modulation mapper #q 230-q (q = 1, ..., Q).

Each of the Q channel encoders 210-1 to 210-Q is configured to receive an information bit and perform channel coding on the information bit to generate an encoded bit. The information bits correspond to the information that the transmitter is to transmit. The size of the information bits may vary according to information, and the size of the encoded bits may also vary according to the size of the information bits and the channel coding scheme. There is no limit to the channel coding scheme. For example, turbo coding, convolution coding, block coding, and the like can be used for the channel coding scheme. The encoded bit in which channel coding is performed on the information bits is called a codeword. Where Q is the number of codewords. The channel encoder #q (210-q) outputs a codeword #q (q = 1, ..., Q).

Each of the Q scramblers 220-1, ..., 220-Q is configured to generate a scrambled bit for each codeword. The scrambled bits are generated by scrambling the coded bits with a scrambling sequence. The scrambler #q (220-q) is configured to generate scrambled bits for the codeword #q (q = 1, ..., Q).

Each of the Q modulation maps 230-1, ..., and 230-Q is formed to generate modulation symbols for each codeword. The modulation symbol may be a complex number symbol. The modulation mapper #q (230-q) is configured to generate a modulation symbol by mapping the scrambled bits for the codeword #q to a symbol representing a location on the signal constellation (q = 1 , ..., Q). There is no restriction on the modulation scheme. For example, m-phase shift keying (m-PSK) or m-quadrature amplitude modulation (m-QAM) may be used for the modulation scheme. The number of modulation symbols for the codeword #q output from the modulation mapper #q (230-q) may vary according to the size of the scrambled bits and the modulation scheme.

The layer mapper 240 is formed to map the modulation symbols for each code word to the R spatial layers. The manner in which the modulation symbols are mapped to the spatial layer may vary. Thereby, R spatial streams are generated. Here, R is a rank. The rank R may be equal to or greater than the number Q of codewords.

The precoder 250 is configured to precode the R spatial streams to produce Nt transport streams. The number Nt of transmission antennas is equal to or smaller than the rank R. [

Each of the Nt transport streams generated by the precoder 250 is input to each of the Nt resource element mappers (see FIG. 5). Each of the Nt transport streams is transmitted through each of the Nt transmit antennas. That is, the transport stream #n is input to the resource element mapper #n and transmitted through the transmission antenna #n (n = 1, 2, ..., Nt).

The MIMO scheme in which multiple spatial streams are simultaneously transmitted through a plurality of transmission antennas is referred to as spatial multiplexing. Spatial multiplexing is spatial multiplexing for a single user and spatial multiplexing for multiple users. Spatial multiplexing for a single user is called single user-MIMO (SU-MIMO) and spatial multiplexing for multiple users is called MU-MIMO. MU-MIMO can be supported in both uplink and downlink.

In the case of SU-MIMO, a plurality of spatial layers are all allocated to one UE. Multiple spatial streams are transmitted using the same time-frequency resource through multiple spatial layers assigned to one terminal.

In the case of MU-MIMO, a plurality of spatial layers are allocated to a plurality of terminals. Multiple spatial streams assigned to multiple terminals are transmitted using the same time-frequency resource. Different terminals are assigned different spatial layers. When the rank is R, R spatial streams can be allocated to K terminals (2? K? R, K is a natural number). Each of the K terminals simultaneously shares time-frequency resources used for transmission of multiple spatial streams.

The dedicated reference signal for multi-antenna transmission may be a precoded RS or a non-precoded RS.

A reference signal that is not precoded is a reference signal that is always transmitted by the number of transmission antennas regardless of the number of spatial layers. The non-precoded reference signal has an independent reference signal for each transmit antenna. Generally, the common reference signal is a reference signal that is not precoded. This is because the precoder is usually used for a specific terminal. However, if there is a cell specific precoder in a particular system, it is considered virtualization, not precoding.

The precoded reference signal is a reference signal transmitted as many as the number of spatial layers. The precoded reference signal has a reference signal independent of each spatial layer.

15 is a block diagram illustrating an example of a transmitter structure that generates a non-precoded dedicated reference signal.

Referring to FIG. 15, the transmitter 300 includes a layer mapper 310, a precoder 320, a RS generator 330, and Nt resource element mappers 340-1,.. ). Here, Nt is the number of transmission antennas of the transmitter 300. Although not shown in FIG. 15, the structure of the transmitter 300 may be referred to FIGS. 13 and 14. FIG. The number of spatial layers is assumed to be R.

The layer mapper 310 is connected to the precoder 320. The precoder 320 and the reference signal generator 330 are connected to Nt resource element mappers 340-1 to 340-Nt, respectively.

The layer mapper 310 is formed to generate R spatial streams (SS # 1, SS # 1, ..., SS #R) for R spatial layers.

The precoder 320 is formed to precode the R spatial streams to generate Nt transport streams TS # 1, TS # 2, ..., TS #Nt.

The reference signal generator 330 generates a reference signal sequence corresponding to the reference signal. The reference signal sequence consists of a plurality of reference symbols. The reference signal sequence may be any sequence, without any particular limitation.

The reference signal generator 330 is configured to generate a reference signal sequence for each of the Nt transmit antennas. The reference signal generator 330 is formed to generate Nt reference signal sequences (RS # 1, RS # 2, ..., RS # Nt). Each of the Nt reference signal sequences includes a plurality of reference signal symbols. The reference signal symbol may be a complex number symbol.

Each of the Nt resource element mappers 340-1, ..., 340-Nt is configured to receive a transport stream and a reference signal sequence and to map the transport stream and the reference signal sequence to the resource elements. The resource element mapper #n 340-n receives the TS #n and the RS #n and maps them to resource elements (n = 1, 2, ..., Nt).

16 is a block diagram illustrating an example of a transmitter structure for generating a precoded dedicated reference signal.

16, the transmitter 400 includes a layer mapper 410, a reference signal generator 420, a precoder 430, and Nt resource element mappers 440-1 to 440-Nt. do. Here, Nt is the number of transmit antennas of the transmitter 400. Although not shown in FIG. 16, the structure of the transmitter 400 can be referred to FIGS. 13 and 14. FIG. The number of spatial layers is assumed to be R.

The layer mapper 410 and the reference signal generator 420 are connected to the precoder 430, respectively. The precoder 430 is connected to Nt resource element mappers 440-1, ..., 440-Nt. The layer mapper 410 is formed to generate R information streams. The R information streams may be represented by IS # 1, IS # 2, ..., IS #R.

The reference signal generator 420 is configured to generate R reference signal sequences. The R reference signal sequences can be represented by RS # 1, RS # 2, ..., RS #R. Each of the R reference signal sequences includes a plurality of reference signal symbols. The reference signal symbol may be a complex number symbol.

An information stream, a reference signal sequence, and a reference signal pattern are allocated to each of the R spatial layers. IS #r and RS #r are allocated to the spatial layer #r (r = 1, ..., R). Here, r is a spatial layer index indicating a spatial layer. The reference signal pattern assigned to the spatial layer #r is a time-frequency resource pattern used for RS #r transmission.

The precoder 430 is formed to precode the R spatial streams to generate Nt transport streams. The R spatial streams can be represented by SS # 1, SS # 1, ..., SS #R. Nt transport streams can be represented by TS # 1, TS # 2, ..., TS #Nt.

Each of the R spatial streams corresponds to one spatial layer. That is, SS #r corresponds to the spatial layer #r (r = 1, 2, ..., R). Each of the R spatial streams is generated based on an information stream, a reference signal sequence, and a reference signal pattern allocated to a corresponding spatial layer. That is, SS #r is generated based on the reference signal pattern allocated to IS #r, RS #r, and spatial layer #r.

17 is a block diagram illustrating an example of a device for wireless communication in which a precoded dedicated reference signal is used.

17, the transmitter 500 includes a precoder 510 and Nt transmit antennas 590-1, ..., 590-Nt. The precoder 510 is connected to Nt transmission antennas 590-1, ..., 590-Nt. The receiver 600 includes a channel estimation unit 610 and Nr reception antennas 690-1, ..., 690-Nr. The transmitter 500 is part of the base station, and the receiver 600 can be part of the terminal.

A MIMO channel matrix H is formed between Nt transmission antennas 590-1, ..., 590-Nt and Nr reception antennas 690-1, ..., 690-Nr. The size of the MIMO channel matrix H is Nr x Nt. If the number of receive antennas is 1, the MIMO channel matrix becomes a row vector. In general, a matrix includes a row vector and a column vector.

The precoder 510 receives R spatial streams. Each of the R spatial streams includes a plurality of spatial symbols. The space symbol may be a complex number symbol. The spatial symbol #k of SS #r can be represented by x r (k) (r = 1, 2, ..., R). The spatial symbols #k of the R spatial streams can be represented by the spatial symbol vectors x (k) = [x 1 (k) x 2 (k) ... x R (k)] T. Where [·] T is a transposed matrix of [·], and k is a time-frequency resource index indicating a time-frequency resource to which a space symbol vector is transmitted. For example, the time-frequency resource indicated by k may be a subcarrier or a resource element.

x r (k) is determined according to the reference signal pattern assigned to the spatial layer #r. x r (k) may be an information symbol of SS #r or a reference signal symbol of RS #r according to the reference signal pattern. Or x r (k) may be set to '0'. Thus, each of the R spatial streams is generated based on an information stream, a reference signal sequence, and a reference signal pattern allocated to a corresponding spatial layer.

The precoder 510 can perform precoding according to the following equation.

Figure 112010017077108-pat00006

Here, z (k) = [z Nt (k) z 1 (k) z 2 (k) ...] T is a transmission symbol vector, W is the precoding matrix of size Nt × R, x (k) = [x 1 (k) x 2 (k) ... x R (k)] T is a space symbol vector. Nt is the number of transmit antennas, and R is rank. When the rank is 1 (R = 1), the precoding matrix becomes a column vector.

The transmitter 500 transmits the transmission symbol vector z (k) through Nt transmission antennas 590-1, ..., 590-Nt.

In the case of MU-MIMO, R spatial layers are allocated to K terminals (2? K? R, K is a natural number). In the case of MU-MIMO, the precoding matrix may be referred to as an MU-MIMO precoding matrix. W is an MU-MIMO precoding matrix, the base station can reconstruct W by receiving CSI (channel state information) fed back from K terminals. Alternatively, the base station may arbitrarily configure W by using CSI that receives W from each of K terminals. CSI means general information on the downlink channel. There is no particular restriction on CSI. The CSI may include at least one of a channel quality indicator (CQI), a precoding matrix indicator (PMI), and a rank indicator (RI). The CQI indicates the MCS level suitable for the channel. The PMI indicates a precoding matrix suitable for the channel. The RI indicates the rank of the channel. The PMI may be a simple matrix index in the codebook. Alternatively, the PMI may be channel quantization information, channel covariance matrix, or the like.

As such, when a precoded reference signal is used, the reference signal symbol of the reference signal sequence for each spatial layer as well as the information symbol of the information stream is also precoded and transmitted.

Receiver 600 receives the received signal vector y = [y 1 y 2 ... y Nr ] T through the Nr receive antennas 690-1, ..., 690-Nr. The received signal vector y can be expressed by the following equation.

Figure 112010017077108-pat00007

Where n = [n 1 n 2 ... n Nr ] T is the noise vector and P = HW is the precoded channel matrix.

The channel estimator 610 may estimate the precoded channel matrix P from the received signal vector based on the precoded dedicated reference signal. Once the precoded channel matrix P is estimated, the receiver 600 may estimate the transmitted information stream for each spatial layer. The receiver 600 can estimate the precoded channel matrix P to demodulate the information even if the receiver 600 can not estimate the MIMO channel matrix H because it can not know the precoding matrix W. [

When such a precoded dedicated reference signal is used, the transmitter need not inform the receiver of the precoding matrix used for transmission. The receiver can apparently demodulate the information even if it does not know the precoding matrix. If a precoded dedicated reference signal is used, the transmitter need not limit the precoding matrix. In general, precoded dedicated reference signals are used to implement non-codebook based precoding.

Precoding may be performed with one precoding matrix over the entire frequency band. This is called wideband precoding. In this case, one precoding matrix is used for one terminal.

However, the channel may be a frequency selective channel or a frequency flat channel. The coherent bandwidth can be used to determine whether the channel is a frequency selective channel or a frequency flat channel based on a coherent bandwidth. The coherent bandwidth is inversely proportional to the delay spread.

In case of a frequency selective channel, the property of the MIMO channel may vary according to a frequency band. As the spatial channel correlation is relatively low, different precoding matrices may be used depending on the frequency band to achieve higher performance gain.

The precoding using different precoding matrices according to frequency bands is called frequency selective precoding. In this case, a multiple precoding matrix may be used for one terminal. When a multiple precoding matrix is used with a precoded dedicated reference signal, the dedicated reference signal must be precoded into a precoding matrix corresponding to the frequency band. Frequency selective coding can be applied not only to the frequency selective channel but also to the frequency flat channel.

In the case of demodulation using a precoded dedicated reference signal, the receiver performs channel estimation only within the resource blocks allocated for information reception. If the receiver is a part of the UE, the UE can know the resource block allocated for information reception through the resource allocation field included in the DL grant. One or more resource blocks may be allocated by the receiver. When a plurality of resource blocks are allocated, the plurality of resource blocks may be allocated consecutively or discontinuously.

If wideband precoding is used, the receiver can perform channel estimation through channel interpolation across the allocated resource blocks. If frequency selective precoding is used, a plurality of precoding matrices may be used in the resource blocks allocated by the receiver. If the receiver can not know the frequency domain in which the coherent precoding matrix is used, the receiver can estimate the channel on a resource block basis. However, since channel interpolation can not be performed over a plurality of resource blocks, channel estimation performance may deteriorate. If the receiver knows the frequency domain in which a consistent precoding matrix is used, then the receiver can channel estimate through channel interpolation in the frequency domain where a coherent precoding matrix is used. When a channel is estimated through channel interpolation, noise and interference can be suppressed, and the channel estimation performance can be enhanced.

Thus, the receiver needs to know information about the frequency domain in which the same precoding matrix is used. The frequency domain in which the same precoding matrix is used may be predefined between the transmitter and the receiver. Or the transmitter may inform the receiver of the frequency region in which the same precoding matrix is used.

18 is a flowchart illustrating a signal transmission method in a wireless communication system according to an embodiment of the present invention.

Referring to FIG. 18, the BS indicates precoding bandwidth information to the MS (step S110). The precoding bandwidth information is information on a frequency region in which a consistent precoding matrix is used. The frequency domain in which a consistent precoding matrix is used may be referred to as a precoding subband. That is, the precoding matrix is the same in the precoding subbands. For example, the precoding subband may be a plurality of contiguous resource blocks or a plurality of contiguous resource elements (or subcarriers). The precoding bandwidth information may indicate the size of the precoding subband. The precoding granularity can be determined according to the size of the precoding subband.

The base station may explicitly indicate, or implicitly instruct, the precoding bandwidth information to the terminal. The base station may explicitly indicate precoding bandwidth information via higher layer signaling, such as physical layer signaling or RRC signaling. For physical layer signaling, the precoding bandwidth information may be transmitted on the PDCCH. In this case, the precoding bandwidth information may be included in the downlink grant.

The base station transmits the precoded signal to the terminal (S120). The precoded signal is a precoded reference signal for each spatial layer and information for each spatial layer.

The terminal estimates the channel based on the reference signal for each spatial layer and demodulates the information for each spatial layer (S130).

In the frequency division duplex (FDD) scheme, the base station can not know the downlink channel characteristics. The terminal estimates the downlink channel and feeds back the CSI for the downlink channel characteristics to the base station on the feedback channel. At this time, the UE can estimate the downlink channel using a common reference signal such as CSI-RS.

In the time division duplex (TDD) scheme, there is a reciprocal channel reciprocity in which the characteristics of the uplink channel and the characteristics of the downlink channel are almost complementary. In the case of the TDD scheme, the UE can also feedback the CSI for the downlink channel characteristics.

The base station can use the feedback CSI for downlink transmission. The CSI includes the PMI, and the BS can transmit information based on the PMI fed back to the UE. Such an information transmission method is referred to as a closed-loop method. In the closed loop scheme, system performance can be improved by transmitting information in a channel adaptive manner.

The base station may not use the feedback CSI for the downlink transmission. Such an information transmission method is referred to as an open-loop method. In the open-loop scheme, the UE may not feed back the PMI.

Frequency selective coding can be used in both closed loop and open loop systems. In the case of the closed loop scheme, multiple precoding matrices may be used to optimize precoding performance according to the frequency band. For an open loop approach, multiple precoding matrices may be used randomly or in a predefined manner. This allows frequency diversity to be increased without feedback to any spatial channel information such as PMI. It is beneficial for the terminal to know the precoding bandwidth information in both closed loop and open loop approaches.

Hereinafter, a method for the BS to indicate the precoding bandwidth information to the UE will be described in detail.

1. Reuse feedback subband definition in closed loop

In the FDD scheme, wideband precoding and frequency selective precoding may be associated with PMI feedback, respectively. The CSI may be channel state information for the entire frequency band or channel state information for the feedback subband which is a part of the entire frequency band.

The precoding subband may be reused for the definition of the feedback subband. The size of the precoding subband is the same as the size of the feedback subband.

The feedback subband may be a plurality of contiguous resource blocks or a plurality of contiguous resource elements (or subcarriers). In general, the feedback subband may be a bundle of resource blocks. For example, the size of the feedback subband may be four resource blocks or eight resource blocks. The size of the feedback subband may vary according to the downlink transmission bandwidth.

The size of the feedback subband may be set by the base station. The base station can set the size of the feedback subband by an upper layer such as RRC. The precoding bandwidth information is implicitly indicated by the size of the feedback subband set by the base station. Or the size of the feedback subband may be predefined between the base station and the terminal. At this time, the size of the feedback subband can be defined in advance according to the downlink transmission bandwidth.

PMI feedback types can have a single PMI type and multiple PMI types. For a single PMI type, the terminal can feed back one PMI over the entire frequency band. For multiple PMI types, the terminal can feed back the PMI by feedback subband. The PMI feedback type can be set by an upper layer such as RRC.

If the PMI feedback type is a multiple PMI type, the size of the feedback subband can be predefined according to the downlink transmission bandwidth.

The following table shows examples of the sizes of the feedback subbands according to the downlink transmission bandwidth (N_DL).

Figure 112010017077108-pat00008

Figure 19 shows an example of a feedback subband for a single PMI type.

Referring to FIG. 19, the downlink transmission bandwidth N_DL is 12. The entire frequency band includes 12 resource blocks (RB # 1, RB # 2, ..., RB # 12). It is assumed that the PMI feedback type is set to a single PMI type by higher layer signaling. The feedback bandwidth is the entire frequency band. The UE feeds back one PMI over the entire frequency band.

Figure 20 shows an example of a precoding subband for a single PMI type.

Referring to FIG. 20, RB # 4, RB # 8, RB # 9, and RB # 11 are resource blocks scheduled for the UE. The terminal is allocated RB # 4, RB # 8, RB # 9 and RB # 11 for information reception. The information on the resource blocks allocated by the UE may be included in the downlink grant. Thus, the UE can discontinuously allocate a plurality of resource blocks.

It is assumed that the PMI feedback type is set to a single PMI type by higher layer signaling. The precoding subband assumes that the definition of the feedback subband is reused. In this case, the precoding bandwidth becomes the entire frequency band. Therefore, the UE can perform channel estimation on all allocated resource blocks (RB # 4, RB # 8, RB # 9, and RB # 11) through channel interpolation.

If multi-carrier is supported, it can be assumed that the same precoding matrix is used for the entire frequency bandwidth in one carrier.

Figure 21 shows an example of a feedback subband for the case of multiple PMI types.

Referring to FIG. 21, the downlink transmission bandwidth N_DL is 12. The entire frequency band includes 12 resource blocks (RB # 1, RB # 2, ..., RB # 12). It is assumed that the PMI feedback type is set to multiple PMI types by higher layer signaling. Referring to Table 1, the size of the feedback subband is 4. Therefore, the feedback bandwidth becomes 4 resource blocks. The UE feeds back one PMI for every 4 resource blocks.

Figure 22 shows an example of precoding subbands for multiple PMI types.

Referring to FIG. 22, RB # 1, RB # 2, and RB # 11 are resource blocks scheduled for the UE. It is assumed that the PMI feedback type is set to multiple PMI types by higher layer signaling. The precoding subband assumes that the definition of the feedback subband is reused. Since the size of the feedback subband is 4, the precoding subband also becomes 4 resource blocks. The UE can expect that a single precoding matrix is used in the precoding subband. Therefore, the UE can perform channel estimation through channel interpolation in the precoding subband.

RB # 1 and RB # 2 are resource blocks included in one precoding subband, and RB # 11 is a resource block included in another precoding subband. Therefore, the UE can perform channel estimation through RB # 1 and RB # 2 through channel interpolation. The UE does not perform channel interpolation with RB # 1 and RB # 2 when channel estimation is performed on RB # 11.

2. Separate precoding bandwidth

Although the base station receives the PMI feedback from the terminal, the base station can use another precoding matrix depending on the preference of the base station. In this case, the precoding subband may be defined separately from the feedback subband. The precoding bandwidth can be defined in various ways. The BS may inform the UE of the precoding bandwidth information, and may be a precoding subband index indicating the precoding bandwidth.

The following table shows an example of a precoding bandwidth according to a precoding subband index when 2 bits are used as a precoding subband index.

Figure 112010017077108-pat00009

The following table shows an example of a precoding bandwidth according to a precoding subband index when 3 bits are used as a precoding subband index.

Figure 112010017077108-pat00010

The maximum precoding bandwidth may be the entire frequency band. In this case, the precoding subband index may indicate wideband precoding. The following table shows an example of precoding bandwidth according to precoding subband index.

Figure 112010017077108-pat00011

The minimum precoding bandwidth may be one resource block. The following table shows another example of the precoding bandwidth according to the precoding subband index.

Figure 112010017077108-pat00012

An N-bit precoding subband index may be included in the downlink rank grant and transmitted on the PDCCH. Or higher layer signaling such as RRC.

3. Pre-coding bandwidth information in open loop

In the open loop scheme, the UE does not need to feed back the PMI. In the case of the open loop method, a higher diversity gain is required as compared with the closed loop method. In one of the diversity modes, precoding matrix switching (PMS) may be used for increasing the diversity gain. The precoding matrix switching may be implemented with matrices in the codebook. The matrices may vary according to precoding subbands. The precoding subband may be defined as one or more resource block levels. Even within one resource block, the precoding matrix can vary. In this case, the precoding bandwidth may be defined as one or more resource element levels. For example, the precoding bandwidth may be six resource elements.

The precoding bandwidth may be determined according to the transmission technique. For example, if the transmission scheme is set to open loop spatial multiplexing, the precoding bandwidth may be defined as k resource blocks. k can be set or predefined by the base station. If k is set by the base station, the base station may indicate k to the terminal via physical layer signaling or higher layer signaling. If the transmission scheme is set to closed loop spatial multiplexing, wideband precoding may be used.

The following table shows examples of different precoding bandwidths for the transmission scheme.

Figure 112010017077108-pat00013

4. Feedback confirmation

The acknowledge bit may be used for frequency selective precoding together with a dedicated reference signal. The acknowledgment bit may indicate whether the precoding subband is the same as the feedback subband. If the base station has indicated PMI feedback by feedback subband, the confirmation bit can determine whether the precoding subband is the same frequency-selective precoding as the feedback subband. The UE can know the precoding bandwidth information through the confirmation bit. The base station may transmit an acknowledgment bit to the terminal through physical layer signaling or higher layer signaling.

5. Unified mode

In both the closed loop and open loop schemes, the base station can indicate the precoding bandwidth through the precoding subband index. The precoding bandwidth according to the precoding subband index can be referred to Tables 2 to 5. However, this is merely an example and does not limit the precoding bandwidth according to the precoding subband index. The precoding subband index may be transmitted to the terminal through physical layer signaling or higher layer signaling.

In the case of the open loop scheme, the base station can limit the available precoding bandwidth. The precoding bandwidth available in the open loop approach may be a subset of the precoding bandwidths available in the Peruvian approach. As shown in the following table, the available precoding bandwidth can be limited in the case of the open loop scheme.

Figure 112010017077108-pat00014

6. Distributed resource allocation

The BS may allocate downlink time-frequency resources to the UE in a distributed manner. The time-frequency resource may be a resource block. The consecutive resource blocks among the resource blocks allocated to the UE are called a resource block group (RB group). Multiple resource block groups may be allocated to the UE. The resource block groups are separated in the frequency domain.

The precoding bandwidth may be started from the first resource block of the resource block group. The precoding bandwidth may be the same as the resource block group. In this case, the UE can obtain the precoding bandwidth information through the resource allocation field included in the DL grant. This allows the base station to flexibly allocate resource blocks to the terminal. In addition, the interpolation gain can be maximized.

23 shows an example of the precoding bandwidth.

Referring to FIG. 23, RB # 4, RB # 5, RB # 9, RB # 10 and RB # 11 are resource blocks scheduled for the UE. RB # 4 and RB # 5 are resource block group # 1, and RB # 9, RB # 10 and RB # 11 are resource block group # 2. The precoding bandwidth # 1 is the same as the resource block group # 1. Therefore, the UE can perform channel interpolation in the resource block group # 1. The precoding bandwidth # 2 is the same as the resource block group # 2. Therefore, the UE can perform channel interpolation in the resource block group # 2.

7. Support for rank-specific precoding bandwidth

Precoding bandwidth can only be supported for rank specific. For example, if the system supports up to Rank 8 transmissions, the precoding bandwidth can only be known for rank 5 or less. This allows flexible scheduling for higher ranks above a certain rank. Also, a channel estimation gain can be provided in a subrank below a certain rank.

8. Layer-specific precoding bandwidth support

When multiple spatial streams are transmitted through multiple spatial layers, the precoding bandwidth indication may be valid only at a specific spatial layer. One resource block based precoding bandwidth may be used in the other spatial layer.

24 is a block diagram illustrating an apparatus for wireless communication in which an embodiment of the present invention is implemented. The base station 50 includes a processor 51 and an antenna 59.

Processor 51 is coupled to antenna 59 to implement the proposed functions, procedures, and / or methods. The layers of the protocol stack may be implemented by the processor 51. The antenna 59 transmits or receives a signal. The antenna 59 may be one or more. The base station 50 may further include a memory (not shown). A memory (not shown) is connected to the processor 51 and stores various information for driving the processor 51. [

The terminal 60 includes a processor 61 and an antenna 69. The processor 61 is coupled to the antenna 69 to implement the proposed functions, procedures and / or methods. The layers of the air interface protocol may be implemented by the processor 61. The antenna 69 transmits the transmission signal or receives the reception signal. The antenna 69 may be one or more. The terminal 60 may further include a memory (not shown). A memory (not shown) is connected to the processor 61 and stores various information for driving the processor 61.

The processors 51 and 61 include an RF (radio frequency) unit for converting an application-specific integrated circuit (ASIC), another chipset, a logic circuit, a data processing device and / can do. The proposed transmitter may be implemented within the processor 51,61. The memory (not shown) may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices. When the embodiment is implemented in software, the above-described techniques may be implemented with modules (processes, functions, and so on) that perform the functions described above. The module is stored in a memory (not shown) and can be executed by the processor 51,61. The memory (not shown) may be internal or external to the processors 51, 61 and may be coupled to the processors 51, 61 by a variety of well known means.

Thus, an efficient signal transmission apparatus and method in a wireless communication system can be provided. The UE can acquire the precoding bandwidth information. The UE can perform channel estimation through channel interpolation in the frequency domain within the precoding bandwidth based on precoding bandwidth information. Thus, the UE can obtain a better channel estimation performance. Thus, overall system performance can be improved.

Those skilled in the art can readily appreciate the additional advantages, objects and features of the present invention through the foregoing description or by implementing the present invention based on the above description. Further, the present invention may have unexpected advantages as a person skilled in the art realizes the present invention based on the above description.

In the above-described exemplary system, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders . It will also be understood by those skilled in the art that the steps shown in the flowchart are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. For example, those skilled in the art can utilize each of the configurations described in the above-described embodiments in a manner of mutually combining them. Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (9)

  1. A method for receiving signals in a terminal of a wireless communication system,
    Obtaining a precoding bandwidth indicating one or more contiguous resource blocks in which a same precoding matrix is used by a base station, wherein the one or more consecutive resource blocks indicated by the precoding bandwidth The size of the resource block being based on a downlink bandwidth allocated by the wireless communication system;
    Receiving, from the base station, a precoded signal through the one or more contiguous resource blocks; And
    Decoding the received signal based on the same precoding matrix
    Containing
    Way.
  2. The method according to claim 1,
    The size of the one or more consecutive resource blocks indicated by the precoding bandwidth is set equal to the size of a feedback subband used for feedback of CSI (channel state information) , The CSI includes at least one of a channel quality indicator (CQI) and a rank indicator (RI)
    Way.
  3. The method according to claim 1,
    The precoding bandwidth is determined according to a transmission scheme set by the terminal
    Way.
  4. In a terminal of a wireless communication system,
    A wireless signal unit for transmitting and receiving wireless signals; And
    Connected to the radio signal unit,
    Obtaining a precoding bandwidth indicating one or more contiguous resource blocks in which a same precoding matrix is used by a base station, wherein the one or more consecutive resource blocks indicated by the precoding bandwidth The size of the resource block is set to be based on a downlink bandwidth allocated by the wireless communication system,
    Receiving, from the base station, a precoded signal through the one or more consecutive resource blocks,
    A processing unit configured to decode the received signal based on the same precoding matrix,
    Containing
    Terminal.
  5. 5. The method of claim 4,
    The size of the one or more consecutive resource blocks indicated by the precoding bandwidth is set equal to the size of a feedback subband used for feedback of CSI (channel state information) , The CSI includes at least one of a channel quality indicator (CQI) and a rank indicator (RI)
    Terminal.
  6. 5. The method of claim 4,
    The precoding bandwidth is determined according to a transmission scheme set by the terminal
    Terminal.
  7. delete
  8. delete
  9. delete
KR1020100024043A 2009-03-30 2010-03-18 Method and apparatus of transmitting signal in wireless communication system KR101753391B1 (en)

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US13/256,432 US9025620B2 (en) 2009-03-30 2010-03-30 Method and apparatus for transmitting signal in wireless communication system
EP10758994.7A EP2415183A4 (en) 2009-03-30 2010-03-30 Method and apparatus for transmitting signal in wireless communication system
JP2012503315A JP5600343B2 (en) 2009-03-30 2010-03-30 Signal transmission method and apparatus in wireless communication system
PCT/KR2010/001907 WO2010114269A2 (en) 2009-03-30 2010-03-30 Method and apparatus for transmitting signal in wireless communication system
CN201080014990.4A CN102379091B (en) 2009-03-30 2010-03-30 Method and apparatus for transmitting signal in wireless communication system
US14/676,700 US9520925B2 (en) 2009-03-30 2015-04-01 Method and apparatus for transmitting signal in wireless communication system
US15/356,042 US9729218B2 (en) 2009-03-30 2016-11-18 Method and apparatus for transmitting signal in wireless communication system

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US20150207550A1 (en) 2015-07-23
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US20170070273A1 (en) 2017-03-09
US9520925B2 (en) 2016-12-13
US9025620B2 (en) 2015-05-05
JP2012522451A (en) 2012-09-20
US20120008587A1 (en) 2012-01-12

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